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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 3 (1998), S. 0 
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: The mean ventricular rate is known to be, on average, higher during episodes of paroxysmal atrial fibrillation (AF) than during the sinus rhythm. The data on other statistical parameters of ventricular periods are less known, especially in the respect of atrial premature beats, which are frequent in paroxysmal AF patients while in sinus rhythm.Methods: This study investigated distinction between paroxysmal AF and sinus rhythm based on statistical parameters of 60-second segments of RR interval series from paroxysmal AF and sinus rhythm episodes. The data of the study were taken from 54 long-term Holter recordings of 31 paroxysmal AF patients. For each segment, the mean, standard deviation, skewness, and kurtosis of RR intervals were computed. The values obtained from segments of paroxysmal AF and sinus rhythm were used in attempts to distinguish both rhythms. The distinction was evaluated using: (1) statistical comparison of each parameter in each tape; and (2) receiver operator characteristics (ROCs) (dependency of specificity on sensitivity) computed in each tape for each individual parameter as well as for multivariate combinations of all four parameters.Results: The comparison found the mean RR to be the most powerful discriminator of all statistical parameters used in the distinction of paroxysmal AF and sinus rhythm. The standard deviation of RR intervals differentiated significantly the segments of sinus rhythm and paroxysmal AF in pool data. However, when applied to individual Holter recordings, the distinction between paroxysmal AF and sinus rhythm based on standard deviation of RR intervals (assessed with ROC) was the worst among all investigated parameters.Conclusions: The study suggests that an automatic distinction between paroxysmal AF and sinus rhythm episodes is highly problematic, mainly because of the frequent atrial premature beats that pollute sinus rhythm episodes in patients with paroxysmal AF.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 3 (1998), S. 0 
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: This study examined the possible role of atrial ectopics and short runs of atrial tachycardia in the initiation of episodes of paroxysmal atrial fibrillation (PAF).Methods: Holter recordings from patients participating in pharmacotherapy trials for the prevention of PAF were examined. Treatment comprised placebo, digoxin, disopyramide, or atenolol. The frequency of atrial ectopic beats during each 30 seconds over the 5 minutes prior to PAF and whether this was also associated with atrial tachycardia (3 or more ectopics in succession) was calculated.Results: The mean number of ectopics was 4.1 in the final minute, but patients receiving disopyramide or atenolol had significantly more ectopics than those on placebo (P 〉 0.05 for both). Those on digoxin had a similar number of ectopics to placebo patients. There was no relationship between heart rate at PAF onset and ectopic frequency, nor any association between the presence of one or more episodes of atrial tachycardia and ectopic frequency.Conclusion: Atrial ectopics increase in frequency prior to PAF onset, and this study suggests that antiarrhythmic therapy may increase the number of ectopics required to initiate PAF.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    British journal of dermatology 140 (1999), S. 0 
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The major histocompatibility complex (MHC) acts as a marker for self during T-cell ontogeny and is associated with the pathogenesis of many autoimmune diseases. Recent investigations have shown about 30% of patients with chronic idiopathic urticaria (CIU) have IgG autoantibodies against the high-affinity IgE receptor, FcεRI, or IgE. A link between MHC class II alleles and CIU has not been reported previously. DNA was extracted from blood of 100 Caucasian patients with CIU, and the MHC class II type determined using the polymerase chain reaction with sequence-specific primers, testing for DRB and DQB1 alleles. The frequency of alleles in CIU patients was compared with that found in 603 controls. Further human leucocyte antigen (HLA) typing on patient subsets, classified by the patients' responses to intradermal injection of autologous serum and their serum-induced histamine release from basophil leucocytes of healthy donors, was undertaken. HLA DRB1*04 (DR4) and its associated allele, DQB1*0302 (DQ8), are raised in CIU patients compared with a control population (P = 2 × 10−5 and P = 2 × 10−4, respectively). HLA DRB1*15 (DR15) and its associated allele, DQB1*06 (DQ6), are significantly less frequently associated with CIU. The HLA DRB1*04 association is particularly strong (corrected P = 3.6 × 10−6) for patients whose serum has in vivo and in vitro histamine-releasing activity. HLA class II typing is consistent with the concept that CIU is a heterogeneous disease, and supports an autoimmune pathogenesis in a subset of patients.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1598-1600 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculate the effects of facet roughness on laser performance of etched-facet semiconductor diode lasers. Facet roughness can be caused by the finite pixel size, used in photolithographic mask fabrication, or in the facet etching process. We consider various sizes of roughness and show that appreciable effects can result from roughness levels previously considered optically flat. Far-field shifts and modal coupling caused by facet roughness are also calculated. Results are highly useful for designing lasers with curved or arbitrarily oriented facts such as unstable resonators or beam steering fan laser diodes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 43 (1995), S. 691-699 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this study, we tested the hypothesis that elevated [CO2] shortens the cell cycle in meristems of Dactylis glomerata, more in a Portuguese population (38°53′N) than in a Swedish population (63°09′N). In the shoot meristem, the cell cycle shortened to about the same extent (∼ 26%) in both populations exposed to the elevated [CO2] treatment. In the root meristem, the cell cycle shortened by 17% in the Portuguese and by 8% in the Swedish population. However, the proportion of rapidly cycling cells increased in the Portuguese much more than in the Swedish population in both meristems. In the root meristem, there was a 1.86-fold increase in the Portuguese compared with a 1.31-fold increase in the Swedish. In the shoot meristem, the increases were 1.5–3-fold for the Portuguese and 1.2-fold for the Swedish. The data are consistent in showing that a major response to the elevated [CO2] treatment was an increase in the proportion of cells that were cycling and that this was more marked for the Portuguese population. A more general response to the elevated [CO2] treatment was a shortening of the cell cycle regardless of population.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The aim was to establish whether temperature and/or elevated [CO2] (-700 μmol mol−1) affects the cell doubling time (cdt) in the different zones of the shoot apex of two natural populations of Dactylis glomerata originating in Portugal (38° S3′ N) and in Sweden (63° 09′ N).In the Portuguese population at ambient [CO2], only the pith rib meristem (PRM) exhibited a significant shortening of cdts from 10 to 30 °C. Elevated [CO2] resulted in a significant shortening of cdt, particularly in the PRM where cdt was reduced 4-8- and 6-1-fold at 10 and 20 °C, respectively, but only 2-fold at 30 °C. In the Swedish population at ambient [CO2], there were no consistent temperature-dependent alterations to cdt and this population was less responsive to elevated [CO2] than the Portuguese population. Nevertheless, elevated [CO2] resulted in a significant shortening of the cdt for some of the zones; the maximum reduction occurred in the PRM at 30 °C.We concluded that in the shoot apex of the Portuguese population, and most notably in the PRM, 10 and 20 °C were non-optimal temperatures for cell division, whilst the Swedish population was relatively buffered against temperature change. Elevated [CO2] resulted in substantially greater reductions in cdts in the shoot meristem of the Portuguese population than in that of the Swedish population.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background and Objective Peripheral blood basophils are reduced in some chronic urticaria patients when counted with granule stains. Approximately 30% of patients with severe chronic urticaria have functional autoantibodies which release histamine from healthy donor basophils in vitro but the relationship between basophil numbers in vivo and serum histamine releasing activity has not been studied.Objective To determine the relationship between basophil numbers and serum basophil histamine releasing activity and to assess whether basophils are present, but undetectable, in peripheral blood with granule stains by using a new Row cytometric method based on surface immunophenotype.Methods Basophils were counted manually by a chamber method using a granule stain and by flow cytometry using dual staining with anti-IgE and anti-FceRI in 25 chronic idiopathic urticaria patients and 25 healthy controls. Serum histamine releasing activity was assessed on healthy donor basophils in vitro and by the weal response to autologous serum skin testing in vivo (patients only).Results Basophils were significantly reduced in chronic urticaria by manual counting and How cytometry. A subgroup of seven patients with in vitro histamine releasing activity showed a marked reduction or absence of basophils by both methods. There were no obvious distinguishing clinical characteristics between these patients and the others; six of them showed positive autologous serum skin-test responses. On comparing the two methods, the manual basophil counts were generally lower than flow cytometric counts. Agreement over the full range of values was not strong and therefore counts obtained by the two methods are not directly interchangeable.Conclusions Basopenia in chronic idiopathic urticaria is associated with serum basophil bistamine releasing activity in a subgroup of patients. The lack of granule and surface immunophenotype staining suggests a reduction in numbers rather than an inability to detect circulating degranulated cells by conventional counting methods.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of digoxin on ventricular response during atrial fibrillation (API and consequent effects on arrhythmic symptoms have still not been fully explained. This study investigated whether the treatment by digoxin contributes to mid– and long–term stabilization of ventricular cycles in patients with paroxysmal AF. A population of 45 patients with paroxysmal AF underwent 24–hour ECG recordings during each arm of a randomized crossover trial comparing digoxin and placebo. This yielded 30 Holter recordings from 22 patients that contained AF episodes lasting in excess of 2 minutes and with acceptably low Holter noise. Each AF episode was divided into nonoverlapping segments of 30 seconds and the distribution of RR intervals in each segment was compared with the distribution of all other AF segments in the same recording using the Kolmogorov–Smimov test. The percentage of tests that revealed significant differences at levels of P ≤ 0.01, and P ≤ 0.001 were sorted according to the time between the segments compared. The comparisons of these results were performed between: (a) all recordings on placebo (n = 16) and all recordings on digoxin (n = 14), and (b) between recordings on placebo and on digoxin in 8 patients in whom paired analysis was possible. Adjacent AF segments (distance 0) differed significantly only in 〈 30% of both recordings on placebo and on digoxin. However, with increasing the distance between segments, the proportion of the significant differences between RR interval distributions increased more with placebo than with digoxin (P 〈 10−300, Chi-square test). Paired data revealed larger differences between placebo and digoxin with increasing distance between segments. Thus in patients with paroxysmal AF, digoxin leads to more reproducible patterns of ventricular cycles that may be better tolerated clinically.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A relationship between autonomic tone and the onset of paroxysmal atrial fibrillation in some patients is recognised Episodes of PAF may vary enormously in duration, however, from a few beats to many hours. Whether autonomic tone influences the duration of ihe episodes has been less well investigated.From a database of Holter recording taken from patients with symptomatic PAF, we identified all episodes of at least 30 seconds duration which were preceded by noise free sinus rhythm. This study examined the heart rate prior to AF onset, the change in heart rate over the final minute of sinus rhythm and the time of AF onset, and compared the data from those episodes of AF of more than 5 minutes duration to the shorter ones. Heart rate was slower before long episodes of AF, but this was found to predominantly represent data from separate recordings. A highly significant rise in heart rate was detected prior to long AF episodes compared to shorter ones. Daytime AF episodes were slightly longer than nocturnal ones.The most important finding was that longer AF episodes were typified by a heart rate acceleration. This suggests that, regardless of underlying aetiology, and increase in sympathetic tone may be important in the sustenance of episodes of PAF.
    Type of Medium: Electronic Resource
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